The specific aim is to study the effects of burn, accidental, and surgical trauma on the Starling pressures (capillary-blood oncotic pressure Pic, interstitial-fluid oncotic pressure Pit, and interstitial fluid pressure Pt). Emphasis will be placed on comparing the efficacy of various resuscitation fluids to maintain fluid homeostasis across the capillary and cellular membranes. The role of intracellular swelling in skeletal muscle ischemia will also be investigated. These objectives will be approached by newly developed techniques for measuring Starling pressures in various tissues of trauma patients and experimental animals. Interstitial fluid pressure Pt will be continuously monitored by the wick catheter technique. Interstitital-fluid oncotic pressure Pit will be measured directly in 1-5 Mul samples of fluid collected by empty wick catheters. Oncotic pressure will be determined in blooc samples collected at various periods in each experimental protocol. Needle biopsies of muscle from the experimental animals and some trauma patients will be used to study fluid shifts across cellular membranes and tissue compliance using morphometric techniques. Human investigations will be made of fluid resuscitation for patients undergoing aortic reconstruction, cardiopulmonary bypass, and following burn injury, long bone fractures, the postural effects on Starling pressures in thorax and ankle, brawny edema following cast removal. In most of these protocols, animal studies will parallel our clinical investigations. Our patient studies will define changes in clinical situations and will allow longitudinal studies and parallel animal experiments will fill in gaps in the clinical studies. Our long-term objective is to identify and quantitate water, protein and electrolyte shifts across capillary and cellular membranes after trauma and subsequent fluid resuscitation to formulate the most effective means of fluid resuscitation for each type of trauma.